Process for the liquid phase direct oxi-
dation of olefins to olefin oxides



United States Patent 3,228,968 PRGCESS FOR THE LIQUID PHASE DIRECT OXI-DATION 0F OLEFINS T0 OLEFIN OXIDES Virgil W. Gash, Ballwin, Mo.,assignor to Monsanto Company, St. Louis, Mo., a corporation of DelawareNo Drawing. Filed Aug. 15, 1962, Ser. No. 216,965 8 Claims. (Cl.260-3485) This invention is directed to a new and improved process forthe preparation of olefinoxides. It is further directed to an improvedsolvent for use as an oxidation medium for the preparation of olefinoxides by the action of molecular oxygen upon olefins.

Still more particularly this invention relates to a process for thedirect epoxidation of olefins with molecular oxygen in a solventcomprising certain carbonic acid esters.

Olefin oxides are extremely useful articles of commerce. They are usedas starting materials for the preparation of anti-freeze compositions,humectants, pharmaceutical preparations, cosmetic formulations, asmonomers for the preparation of polymers useful in preparingpolyurethanes, and the like. Notable among these epoxides are ethyleneoxide and propylene oxide. Currently these are prepared by a vapor phasecatalytic method and by the classic two-step chlorohydrin route,respectively. The vapor phase process insofar as industrial productionof epoxides is concerned, is confined to the preparation of ethyleneoxide. Higher olefins have yet to be used in a vapor phase catalyticprocess to give economic production of the corresponding oxides. Theolder chlorohydrin route is the principal industrial process whichsupplies the largest quantities of propylene oxide for commerce. Thisprocess is suitable for conversion of ethylene and propylene to theircorresponding epoxides, but higher olefins are not particularlyadaptable to the chlorohydrin route.

Still a third process for preparation of olefin oxides is that involvingperacetic acid oxidation of olefins to the corresponding oxides. Thisprocess appears to have wider application insofar as olefin structure isconcerned than do the first two methods mentioned. It apparentlyproceeds by an ionic mechanism, and the rate of epoxidation usingperacetic acid is characteristic of the structure of the olefin. Forexample, highly substituted ethylenes, such as tetramethylethylene andtrimethylethylene, react smoothly and rapidly with peracetic acid togive the corresponding epoxides. However, ethylenic compounds havingmuch lower degrees of substitution about the carbon to carbon doublebond, for example, ethylene and. propylene, by virtue of the ionicnature of the reaction, react sluggishly with peracetic acid and therate of formation of the corresponding epoxides is very slow.

Nevertheless, each of these aforementioned processes has inherentdisadvantages. For example, vapor phase catalytic oxidation of ethyleneto ethylene oxide requires large volume equipment and the handling oftremendous quantities of potentially explosive mixtures of ethylene andoxygen. The second process, that is, the chlorohydrin route, forpropylene oxide essentially involves a twostep process; in addition,chlorinated by-products arise in this process. The third process,involving peracetic acid oxidation of olefins, is potentially hazardousif relatively large quantities of peracetic acid are to be used. It isnoted, however, that the peracetic acid process is probably the mostversatile of the three methods; it is applicable to a far greater rangeof olefin structures than is the vapor phase catalytic process or thechlorohydrin process.

There are scattered references to still a fourth method of preparingolefin oxides, namely the liquid phase oxida- "ice tion of olefins withmolecular oxygen. Several of these are restrictive in the sense thatspecific limitations are incorporated in each method. For example,catalysts or other additives or secondary treatment of the oxidationmixtures with basic materials are essential features of these methods.

Since the present invention is concerned with a novel liquid phaseepoxidation system, the discussion below will be directed to typicalexisting prior art schemes for liquid phase olefin oxidations. Theseprior art processes describe a variety of approaches to a proper balanceof a series of reaction variables in order to obtain the desired olefinoxide. For example, various specific oxidation catalysts orcatalyst-solvent systems have been described (US. Patents 2,741,623,2,837,424, 2,974,161, and 2,985,668); another approach is theincorporation of oxidation anticatalysts which retard certainundesirable side reactions (US. Patent 2,279,470); still anotherapproach emphasizes the use of water-immiscible hydrocarbon solventsalone, or in the presence of polymerization inhibitors such asnitrobenzene (US. Patent 2,780,635); or saturated hydrocarbons (US.Patent 2,780,634); another method describes the use of neutralizers suchas alkali metal and alkaline earth metal hydroxides, or salts of thesemetals (U.S. Patent 2,838,524); another approach involves the use ofcertain catalysts in an alkaline phase (US. Patent 2,366,724), or aliquid phase maintained at specified critical pH values (U.S. Patent2,650,927); and still other approaches emphasize criticality of oxygenpressure (US. Patent 2,879,276), or the geometry of the reaction zone(US. Patents 2,530,509 and 2,977,374). The foregoing represent prior artapproaches to problems encountered in the utilization of a liquid phaseoxidation process to obtain olefin oxides.

It is the primary object of the instant invention to provide a superiorprocess for commercial production of olefin oxides which process is freeof numerous limitations recited in prior art processes.

A further object of this invention is to provide a liquid phase processfor the production of olefin oxides which is not dependent upon thepresence or absence of any catalyst; nor dependent upon the presence ofwaterimmiscible solvents or upon solvents containing added bui'fers oracid neutralizers or other additives or secondary treatments withalkaline materials to remove acidic components; nor is it dependent uponthe presence of saturated compounds, initiators or anticatalysts;further it is not dependent upon critical reactor geometries,temperatures, pressures, pH level, oxygen concentration, flow rates, orreactant ratios.

It is a further object of this invention to provide a new class ofsolvents for direct epoxidation of olefins with molecular oxygen.

It is an additional object of this invention to provide a new processwhich is applicable to a wide range of olefin structures; that is, it isnot limited to a single olenfin or two, but rather, has a broadapplication over a large class of unsaturated compounds.

It is an additional object of this invention to provide a new processwhich requires relatively small scale equipment and does not involve thehazards associated with certain of the prior art processes, e.g., thevapor phase process.

Other objects of this invention are to provide a process for productionof olefin oxide in bat-ch or continuous manner by a method which issimple, safe, economical and dependable.

These and other objects of the invention will become apparent to thoseskilled in the art as description of the invention herein proceeds.

According to the present invention, it has been discovered that oleflnscan be oxidized to epoxides with molecular oxygen in high conversionsand yields when the oxidation is allowed to proceed in a liquid reactionmedium comprising carbonic acid esters having the foland mixturesthereof, wherein R, R and R" represent hydrogen, straight chain alkyland haloalkyl groups having from 1 to 3 carbon atoms or straight chainalkyl and haloalkyl groups having from 1 to 3 carbon atoms having assubstituents on other than the terminal carbon atom thereof one or morealkyl or haloalkyl groups having from 1 to 3 carbon atoms. An essentiallimitation upon the selection of carbonic acid esters for use herein isthat the carbon atoms to which the R, R and R" are attached in the aboveformulae have not more than one methylene (CH group attached thereto.The acyclic carbonate may be symmetrical in which caseall Rs and all R'swill be identical or the carbonate may be asymmetrical, e.g., where allRs are hydrogen and the R groups may be alkyl or haloalkyl according tothe above definition. The Rs and/or R's may all be alike or different.In the cyclic carbonates above, the R"s may all be hydrogens, identicalalkyls or haloalkyls according to the above limitations or the Rs may bemixtures of these groups.

It is a characteristic feature of the specific group of carbonic acidesters disclosed herein that no labile hydrogen atoms be present on thecarbon atoms attached to the oxy oxygen (O) atoms and that not more thanone methylene group be attached to said carbon atoms. It is a feature ofthe instant solvents that the bonds between the carbon atoms (of thealcohol moiety) and the hydrogen atoms attached thereto are protectedagainst cleavage by a screening effect or steric hinderance alforded bythe presence of stable groups attached to or proximate to said carbonatoms and also, in the case of the cyclic carbonates, by the carbonatemoiety. Preferably, the stable groups attached to said carbon atom aremethyl radicals or branched chain groups having no labile hydrogenatoms. However, one methylene group or a tertiary hydrogen maypermissibly be attached to said carbon atom. So that in operableembodiments a carbonic acid ester according to the above general formulacan have a four-carbon straight chain alkyl group with up to threemethylene groups or an isopropyl group as the alcohol moiety of theester. In these embodiments, hydrogen atoms are attached to the carbonatom adjacent to the oxy oxygen, but because of the proximity of stablemethyl groups the hydrogen atoms :are stabilized against abstraction byoxygen atoms.

Typical acyclic carbonate esters suitable herein include dimethylcarbonate, ditertiarybutyl carbonate, bis(dimethyltrichloroethyl)carbonate, methyl 1,1-didimethyl carbonate, bis( 1,1,3 trimethyl3-bromobutyl) carbonate, methyl tertiarybutyl carbonate, diethylcarbonate, dipropyl carbonate, ethyl isopropyl carbonate, and the like.

Of the acyclic carbonic acid ester solvents disclosed herein the mostpreferred member is dimethyl carbonate because of its ease ofpreparation and ready availability. Typical cyclic carbonate esters(also called dioxolanes) suitable herein include ethylene carbonate,4-methyl-2- oxo-l,3-dioxolane, 4,5-dimethyl-2-oxo-l,3-dioxolane, 4,5-ditertiarybutyl 2 oxo-l,3-dioxolane, 4-methyl-5-tertiarybutyl2-oxo-1,3-d ioxolane, 4-(1,1-dimethyl-2,2,2-trichlo- I) thyXO-1,3-di0x0lane, ,5, -tetramethyl-2-oxo- 1,3 dioxolane,4-(1,1,3-trimethyl-3-bromobutyl)-2-oxo- 1,3 dioxolane,4-trifluoromethyl-2-oxo-l,3-dioxolane and the like. These esters arereadily prepared by means known to the art, e.g., by reaction ofphosgene (C001 with alcohols. Mixed esters are obtained by reaction of achlorocarbonic ester with an alcohol.

The carbonate solvents contemplated in the present invention aresuitably used individually or as mixtures of carbonates. For example,dimethyl carbonate mixed in varying proportions with ethylene carbonateis a suitable oxidation solvent according to the present invention. Inlike manner, mixtures of acyclic carbonates or mixtures of cycliccarbonates are useful combinations herein.

The solvents contemplated in the present invention combine essentialcharacteristics and features required for successful liquid phaseoxidation, that is, they are essentially chemically indifferent and areoxidatively and thermally stable. Furthermore, the instant solvents aresuperior to those disclosed in prior art liquid phase olefin oxidationprocesses in that they do not require buffers, neutralizers, initiators,inhibitors and /or catalysts in order to utilize the above-mentionedessential to effect oxidation of the olefin to the olefin oxide in highyield and conversion. The solvents of prior art processes requirebuffers, neutralizer, initiators, inhibitors and/ or catalysts in orderto promote the oxidation of the olefin and combat the deleteriouseffects of by-products such as acid components.

It is known that olefin oxidations give, in addition to epoxides,various 'by-products such as water, formic acid and acetic acid whichcan be deleterious to the oxidation when present in appreciablequantities by reacting with the olefin oxide to give correspondingglycol and glycol derivatives as well as undesired polymeric materials.Prior art methods have used a variety of approaches to counteract thesedeleterious effects, such as the use of water-immiscible hydrocarbonsolvents containing inhibitors or utilized in conjunction with aseparate washing step with solutions of basic substances, in effect,processes which require acid removal in order for such water-immisciblehydrocarbon solvents to be used for the olefin oxidation.

Probably the most deleterious constituent is formic acid which by virtueof its strong acidity (stronger than acetic acid by a factor of 10)reacts with the desired olefin oxide to form undesirable 'by-products.It has been found that acetic acid, unlike formic acid, can be toleratedin the reaction mixture of this invention in much greater amounts thanformic acid without producing any adverse eifects. One way to remove thereactive formic acid from the reaction mixture is by salt formation,that is, by addition of an organic or inorganic base. However, thesebasic compounds are known to inhibit primary oxidation reactions andtherefore cannot suitably be used. The formation of salts likewisepresents additional mechanical problems due to a build-up thereof in thereact-or and salt removal systems must be resorted to.

A feature of the present invention is the scavenging of the deleteriousformic acid as it is produced in the reac tion through the use of anester of the class described herein, such as dimethyl carbonate. Anadvantage of using these esters as an acid scavenger is that a stable:neutral material, i.e., the ester is used to remove the: strong formicacid by ester interchange and at the same.- time yield relativelyinnocuous products.

In order to use the presently described esters as an oxidation solvent,the acid and alcohol moieties that make up the ester must have inherentoxidative and thermal stability or these properties must arise as theresult of ester formation between the two moieties. The oxidativestability herein referred to has reference to the stability of thesecompounds toward air or molecular oxygen. In making reference to theoxidative stability of a particular compound it is necessary to makereference to the oxidizing agent, that is, the oxidants used in. thereaction. Some compounds stable to chromic acid or potassiumpermanganate are not stable to other oxidizing agents. For example,alkaline hydrogen peroxide is a specific oxidant for epoxidation ofconjugated double bonds. Yet, the instant esters are not a suitablemedium for the use of alkaline hydrogen peroxide in epoxidation of suchdouble bonds because the esters react with the alkali to form a metalsalt without production of epoxide.

Oxidation substrates also behave difie-rently with respect to theoxidant being used. For example, the acidcatalyzed reaction of peraceticacid or pe-rbenzoic acid with cyclohexene will yield the epoxide.However, the reaction of nitric acid or permanganate on the samesubstrate will yield diiferent products, e.g., using photoxidation withlight in the presence of a catalyst, the methylone group adjacent to thedouble bond is attacked to give a hydroperoxide and the double bond isnot attacked. Hydrogen peroxide whether acidic or basic or as the rarelyused neutral compound is known not to attack methylene groups. On theother hand, these groups are susceptible to attack not only by molecularoxygen, but also by nitric acid, ch-romic acid, permanganates and manyother stronger oxidants. It is for these reasons that the esters used inthe present invention must be those which do not contain reactivemethylene groups or labile hydrogen atoms on the carbon atom adjacent tothe oxy oxygen, i.e., the carbon atom of the alcohol moiety.

It is a primary feature of the present invention that the carbonic acidester solvents used herein need no added substances to counteract thedeleterious effect of Water and acids. Furthermore, the solvents usedherein for the olefin oxidation have appreciable co-solubility withwater, hence, avoid the problems engendered with a two phase reactionsystem arising from the use of water-immiscible solvents. Moreover, byuse of the instant solvents a surprisingly substantial quantity of waterand organic acids can be tolerated without undue adverse effects uponthe course of the olefin epoxidation.

It is a further feature of the instant invention that the olefinoxidations proceed at such a rapid rate that the oxygen isquantitatively consumed, hence, accumulation of potentially hazardouexplosive mixtures of oxygen and organic materials in the vapor stateare avoided.

It is further apparent that there is no criticality insofar as pH valueis concerned for this oxidation since appreciable concentrations of acidby-products, for example, up to weight percent of acetic acid is notparticularly deleterious. Hence, the olefin oxidation in the presentsolvents proceeds suitably over a range of pHs as low as pH4 and inneutral and alkaline pH ranges.

Substantial evidence exists that these olefin oxidations, for example,propylene to propylene oxide, by direct oxidation with molecular oxygenare propagated by a free radical chain mechanism. Copper and itscompounds are strong inhibitors for this propylene oxidation; aninhibition probably due to a redox reaction of copper with peroxyradicals which interrupts the chain propagation sequence and preventsattainment of a long kinetic chain necessary for reasonable conversionof the olefin. In addition, when free radical inhibitors, that is,antioxidants are added to the reaction mixture, partial or completeinhibition of the olefin oxidation occurs. In the absence of suchinhibitors a very rapid, vigorous exothermic oxidation of the olefinoccurs in the solvent. Furthermore, the present solvents are apparentlyvery resistant to free radical attack and are recovered substantiallyunchanged. On the contrary, among prior art solvents benzene is anexample of a compound which is readily attacked by free radicals. Such abenzene radical can react with oxygen to give phenolic or quinonoid-typemolecules which are known to be efficient inhibitors for radical chainoxidations. Thus, when benzene is used as a solvent for an olefinoxidation its susceptibility to free radical attack gives rise to aneffect which might be called autoinhibition, that is,

the rate of oxidation of the olefin decreases with time. In comparison,the carbonic acid ester solvents described herein have a high order ofresistance to radical attack, do not impede the radical chain sequenceand the rate of oxidation of the olefin is not affected; the olefinoxidation proceeds to the depletion of either the olefin or the oxygen.

The carbonic acid ester solvents used in the instant inventionconstitute a suitable reaction medium for substantially all olefinoxidations with molecular oxygen to form olefin oxides. The termmolecular oxygen as used herein includes pure or impure oxygen as wellas gases containing free oxygen, for example, air.

Olefins suitable for use herein preferably include those of theethylenic and cycloethylenic series up to 18 carbon atoms per molecule,e.g., ethylene, propylene, butenes, pentenes, hexenes, heptenes,octenes, nonenes, dodecenes, pentadecenes, heptadecenes, octadecenes,cyclobutenes, cyclopentenes, cyclohexenes, cyclooctenes, etc. Of particular interest, utility and convenience are the olefins containingfrom 2 to 8 carbon atoms. Included are the alkylsubstituted olefins suchas Z-methyl-l-butene, 2-methyl-2- butene, Z-methyl-propene,4methyl-2-pentene, 2-ethyl-3- methyl-l-butene, 2,3-dimethyl-2-butene and2-methyl-2- pentene. Other suitable olefinic compounds includehydrogenated phthalic anhydrides, such as dihydroand tetrahydrophthalicanhydrides. Still other suitable olefins include butadiene, isoprene,other pentadienes, hexadienes, heptadienes, octadienes, decadienes,octadecadienes, alkyl and polyalkyl-substituted cycloalkenes andcycloalkadienes, vinyl-substituted cycloalkenes and benzenes,cyclopentadiene, dicyclopentadiene, styrene, methystyrene,alkylrnethylstyrene, and other vinyl-substituted aromatic systems.Another class of olefinically unsaturated compounds which are ofinterest in this direct expoxidation to epoxides are the unsaturatedmacromolecules, that is, the rubbers, such as butadiene polymers,isoprene polymers, butadiene-styrene copolymers, isobutylene-isoprenecopolymers, chloroprene polymers and other copolymers in corporatingdienic and vinyl comonomers therein, and the like.

Particularly suitable olefin feed stocks contemplated in the instantinvention include the pure olefin or mixtures thereof or olefin stockscontaining as much as 50% of saturated compounds. Olefinic feedmaterials include those formed by cracking petroleum stock such ashydrocarbon oils, paraffin wax, lubricating oil stocks, gas oils,kerosenes, napthas and the like.

The reaction temperatures used in liquid phase olefin oxidations usingthe solvents of the instant invention are subject only to a lower limitbelow which the oxidation either proceeds too slowly or follows a courseother than that leading to olefin oxides. The upper limit of the tem-'perature range is that which may be termed a threshold above whichsubstantial decomposition, polymerization or excessive oxidative sidereactions occur, thereby leading to undesirable side reactions andproducts which substantially detract from the yield of the olefin oxide.In general, temperatures of the order of C. to 350 C. are contemplated.It is expedient to maintain temperatures at a sufficiently high level toinsure thermal decomposition of hazardous peroxides which may be formedand accumulated to the point of unsafe operation. Within this generaltemperature range preferred temperatures are within the range of to 250C.

Subatmospheric, atmospheric or superatmospheric pressures are suitablefor use in the instant invention, that is, ranging from 0.5 to 350atmospheres. Usually the oxidation reaction is facilitated by the use ofhigher pressures, hence a preferred pressure range is from 6 toatmospheres. Pressures herein delineated and temperatures describedpreviously will generally be selected, of course, depending upon thecharacteristics of the individual olefin which is to be oxidized to theolefin oxide,

but this combination of temperatures and pressures will be such as tomaintain a liquid phase. Olefin oxidations in the instant solvents areautocatalytic, that is, they are free radical chain reaction mechanisms,and the reactions proceed very rapidly after a brief induction periodand give remarkably constant product composition over wide variations ofconditions. A typical olefin oxidation, for example propylene in batchoperation, requires from about 1 to 20 minutes. Similar, or faster,reaction rates occur in continuous operation. The reaction vessel forconducting this olefin oxidation can be made of materials which mayinclude almost any kind of ceramic material, porcelain, glass, silica,various metals, such as stainless steels, aluminum, silver and nickel,which vessels do not necessarily have to conform to any particulargeometric design. It should be noted in the instant invention that noadded catalysts are necessary and no reliance is placed upon catalyticactivity of the walls of the reactor or reactor components.

Various means known to the art can be utilized for establishing intimatecontact to the reactants, i.e., olefin and molecular oxygen in thesolvent, for example, by stirring, sparging, shaking, vibration,spraying or other various agitation in the reaction mixture. Thevigorous agitation of the reaction mixture effects not only intimatecontact of olefin and oxygen, but also facilitates removal of the heatof reaction to suitably oriented heat exchangers. It is to be noted,also, that the exothermic nature of the olefin oxidation is such thatvery small or negligible amounts of heat need be applied to the reactionsystem in order to maintain the desired temperature of operation, hence,reaction temperature is adequately maintained by suitable design andproper use of heat exchange components.

As noted above, no added catalysts are required in the presentinvention. The usual oxidation catalysts can be tolerated althoughusually no significant benefit accrues from their use because the olefinoxidation proceed in such facile manner in the solvents of the instantinvention. Oxidation catalysts such as platinum, selenium, vanadium,manganese, silver, cobalt, chromium, cadmium and mercury in metallic orcompound form, preferably as oxide or carbonate or as soluble acetatesor carboxylates may be present singly or mixed in gross form supportedor unsupported or as finely-divided suspensions or in solutions in thesolvent.

It should also be noted that since olefin oxidations according to thisinvention proceed at such a rapid rate after a brief induction period noinitiators, accelerators, or promoters are required, but these may beused to shorten or eliminate the brief induction period after which noadditional initiator, promoter or accelerator need be added. Suitableinitiators, accelerators or promoters include organic peroxides such asbenzoyl peroxide, teitiarybutylhydroperoxide, ditertiarybutyl peroxide;inorganic peroxides such as hydrogen and sodium peroxides; organicperacids such as peracetic and perbenzoic acid or various otherperoxidic derivatives such as the hydroperoxide addition products ofketones and aldehydes. Also useful as initiators, promoters, oraccelerators for the purpose of reducing the time of the inductionperiod, but following which induction period no more need be added arereadily oxidizable materials such as aldehydes, e.g., acetaldehyde,propionaldehyde, isobutyraldehyde and the like and ethers such asdiethyl ether, diisopropyl ether.

The reaction mixtures to be used in carrying out the A solvent mixtureincrementally or continuously. Or, the reactor may be charged withsolvent and the olefin and oxygen gas may be introduced simultaneouslythrough separate feed lines into the body of the solvent in a suitablereaction vessel. In one embodiment the olefin and oxygen-containing gasmixture is introduced into the solvent in a continuously stirredreactor, under the conditions of temperatures and pressures selected forthis particular olefin. Suitable olefin-to-oxygen volumetric ratios arewithin the range of 1 to 5 up to 15 to 1. Feed rates, generally, ofoxygen or oxygen-containing gas may vary from 0.5 to 1500 cubic feet perhour or higher and will largely depend upon reactor size withinproduction quantity desired. The oxygen input is adjusted in such manneras to allow virtually complete usage of oxygen, thereby keeping theoxygen concentration in the off-gas above the reaction mixture belowabout 1%. Obviously this safeguard is necessary in order to prevent ahazardous concentration of explosive gases, as is well known in the art.Proper adjustment of feed rates is of importance in order that theolefin not be stripped from the liquid phase, thus reducing itsconcentration, hence reducing the rate of oxidation of the olefin whichwould result in lower conversion-s per unit time of olefin to olefinoxide. The solvents used herein represent the predominant constituent inthe reaction mixture, with respect to all other constituents, includingreactants, oxidation products and by-products. By predominant is meantenough solvent is always present to exceed the combined weight of allother constituents. In other words, the reaction mixture comprises majoramounts of the solvent and minor amounts of all other constituents withrespect thereto.

The oxidation products are removed from the reactor as a combined liquidand gaseous effluent containing the olefin oxide, unreacted componentsand by-products, by properly adjusting conditions of temperature andpressure and by adjustment of a let-down system, or the entire reactionmixture containing the oxidation products is removed from the reactor;conventional techniques for separation of desired product includingdistillation, fractionation, extraction, crystallizations and the like,are employed to effect sepanation of the desired olefin oxide. Oneprocedure comprises continually removing the liquid efiluent from thereaction zone to a distillation column and removing various fractions ofproducts contained therein, in effect, a fractionation to obtain theolefin oxide. From such suitable fractionation process the solvent isrecovered and is recycled to the reaction zone.

The invention will be more fully understood by reference to theillustrative specific embodiments presented below.

A modified cylindrical Hoke high pressure vessel is employed for thebatch-type oxidations described below. A high pressure fitting waswelded to the vessel near one end to serve as gas inlet, and a blockvalve with rupture disc was attached to this fitting with a onequarterinch high pressure tubing goose-neck. A thermocouple was sealed into oneend opening of the vessel. The solvent and initiator (if any employed)are then charged through the other end opening which is then sealed withthe plug. The olefin is then charged to the desired amount, asdetermined by weight difference, that is, the olefin, if normallygaseous, is charged under pressure, and if normally liquid, may becharged into one of the end openings along with solvent. The chargedvessel is aifixed to a bracket attached to a motor driven eccentricwhich provides vertical vibrational agitation. The tubular Hoke vesselis clamped in a horizontal position in order that the maximum agitationof contents is obtained. This vibrating reaction vessel can be immersedin a hot bath for heating to reaction temperatures and removed, thenimmersed in a cold bath to quench to room temperature.

Example I This example illustrates the oxidative and thermal stabilityof dimethyl carbonate, a typical carbonic acid ester according to thepresent invention.

To a 150 ml. pressure vessel fitted with a thermocouple, rupture disc,and gas inlet fitting was charged 20.6 g. of dimethyl carbonate and 20mg. of mercuric acetate. The reactor was sealed, mounted on an agitatorassembly and immersed in an oil bath at 200 C. When thermal equilibriumwas reached, oxygen was admitted to the reactor .to a total overpressureof 200 p.s.i.g. over a period of 15 minutes. The dimethyl carbonate wasfound to be completely stable, both thermally, and oxidatively.

Example II To a pressure vessel similar to the one described above Wascharged 19.6 g. of dimethyl carbonate, 7.8 g. of propylene, drops ofacetaldehyde, and 20 mg. of mercuric acetate. The reactor was sealed,mounted on an agitator assembly and immersed in an oil bath at 180 C.When thermal equilibrium was reached, oxygen was admitted initially at50 p.s.i.g. over autogenous pressure and gradually increased to 200p.s.i.g. during a 17 minute reaction period. The thermal pattern showeda maximum temperature rise of C. over bath temperature with reactiontemperature being at least 190 C. (a AT of 10 C. over bath temperature)for of the total reaction period. This thermal pattern indicates asubstantial production of oxygenated products from propylene. The oxygenfeed was shut off and the reactor was immersed in a cold water bath.Chromatographic analyses of the reactor contents showed acetaldehyde,methanol, methyl acetate, acetone, formic acid, acetic acid and wateramong the oxygenated products and including propylene oxide as the majorconstituent.

Example III To a pressure vessel of the type described above Was charged21.3 g. of dimethyl carbonate, 10 drops of acetaldehyde, and 8.3 g. ofpropylene. The sealed reactor was mounted on an agitator assembly andimmersed in an oil bath at 175 C. When thermal equilibrium was attained,oxygen was introduced into the reactor gradually to an overpressure of200 p.s.i.g. over a reaction interval of 10 minutes. A maximumtemperature of 195 C. (a AT of 20 C. over bath temperature) was obtainedand the reaction temperature was still 10 over bath temperature at theend of the 10 minute reaction period. This thermal pattern indicates asubstantial production of oxygenated products from propylene. The oxygenfeed was shut off and the reactor was immersed in a cold water bath.Chromatographic analyses of the reactor content showed a 43.5%conversion of propylene to oxygenated products including a 4.9% yield ofmethyl formate, a 23.2% yield of propylene oxide, an 8.6% yield ofmethanol, and 10% yields respectively of water and carbon dioxide.

Example IV To a pressure reactor of the type described above is charged30 g. of dimethyl carbonate, .13 g. of acetaldehyde as an initiator, andabout 5 g. of ethylene. The sealed reactor is attached to an agitatorassembly and immersed in a hot oil bath of 220 C. When thermalequilibrium is established Within the reactor, oxygen is introduced to atotal overpressure of 200 p.s.i.g. The oxidation is carried on for about7 minutes, then the oxygen is shut oil and the reactor is immersed in acold water bath. Analyses indicate a 15% conversion of ethylene tooxygenated products including a 23% yield of ethylene oxide.

Example V To a similar reactor is charged 25 g. of dimethyl carbonate,10 drops of acetaldehyde as an initiator, and about 6 g. of2-methyl-2-butene. The sealed reactor is attached to an agitatorassembly and immersed in an oil bath at C. When thermal equilibrium isreached within the reactor, an oxygen overpressure of 100 p.s.i.g. isintroduced to initiate the reaction followed after a 2 minute intervalby an additional 100 p.s.i.g. overpressure of oxygen. After a totalreaction period of approximately 8 minutes, oxygen addition is stopped,and the reactor is cooled in a cold water bath. Analyses indicate a 35%conversion of olefin to oxygenated products with a major product being2-methyl-2,3-epoxybutane obtained in about 49% yield.

Example VI To a pressure vessel similar to the above described reactorsis charged 35 g. of dimethyl carbonate, 10 drops of acetaldehyde asinitiator, and about 7 g. of styrene. The sealed vessel is attached toan agitator assembly and immersed in an oil bath at C. After thermalequilibrium is reached within the reactor, oxygen is added graduallyover approximately a 10 minute reaction period to a total oxygenpressure of 200 p.s.i.g. The reaction is terminated by oxygen shut-offand analyses of the reaction products indicate a 46% conversion ofolefin to oxygenated products among which styrene oxide is the majorconstituent.

Example VII To a pressure reactor is charged dimethyl carbonate,acetaldehyde, initiator, and b utadiene. The sealed reactor is attachedto an agitator assembly and immersed in an oil bath at C. After thermalequilibrium is obtained, oxygen is introducedto a total overpressure of200 p.s.i.g. over a reaction interval of about 10 minutes. The oxygen isthen shut off and the reactor is cooled by immersion in a cold waterbath. Analyses indicate a 57% conversion of olefin to oxygenatedproducts containing butadiene oxide in about 17% yield.

Example VIII This example illustrates a continuous run using dimethylcarbonate as solvent.

A one-liter stirred stainless steel reactor is employed, fitted withthree fed lines to introduce olefin, oxygen, and dimethyl carbonatesolvent into a bottom inlet in the reactor. A product overfiow pipedrains gaseous and liquid products continuously into a separationsystem. Using dimethyl carbonate as solvent, the reactor is heated to200 C. and propylene is charged to about 25% by weight of the solvent.The reaction is initiated by incremental additions of oxygen, then thethree reactants are metered into the reactor as the oxidation productsare removed continuously. In a typical run, the reactants are added atapproximately the following hourly rates: propylene, 450 g., oxygen, 170g., dimethyl carbonate, 3500 g. At a steady reaction state, with aresidence time of about 5.5 minutes, propylene conversion is 47%, oxygenconversion is 98% or better, and propylene oxide yield is better than40%.

Example IX To a pressure vessel similar to that described above ischarged 20 g. of methyl t-butyl carbonate, about 8 g. of propylene, 10drops of a-cetaldehyde, and 20 mg. of mercuric acetate. The reactor issealed, mounted on an agitator assembly and immersed in an oil bath at180 C. When thermal equilibrium is reached, oxygen is admitted initiallyat 50 p.s.i.g. over autogenous pressure and gradually increased to 200p.s.i.g. during about 17 minute reaction period. The thermal patternshows a maximum temperature rise of 15 C. over bath temperature withreaction temperature being at least C. (at AT of 10 C. over bathtemperature) for most of the total reaction period. This thermal patternindicates a substantial production of oxygenated products frompropylene. The oxygen feed is shut oil and the reactor immersed in acold water bath. Chromatographic analyses of the reactor contents showacetalde- 11 hyde, methanol, methyl acetate, acetone, formic acid,acetic acid, water and propylene oxide among the oxygenated products,the propylene oxide being the major constituent.

Example X To a pressure vessel of the type described above is charged21.3 g. of ethylene carbonate, 10 drops of acetaldehyde, and about 8 g.of propylene. The sealed reactor is mounted on an agitator assembly andimmersed in an oil bath at 175 C. When thermal equilibrium is obtained,oxygen is introduced into the reactor gradually to an overpressure of200 p.s.i.g. over a reaction interval of about 10 minutes. A maximumtemperature of 195 C. (a AT of 20 C. over bath temperature) is obtainedand the reaction temperature is still 10 over bath temperature at theend of approximately a 10 minute reaction period. This thermal patternindicates a substantial production of oxygenated products frompropylene. The oxygen feed is shut off and the reactor immersed in acold water bath. Chromatographic analyses of the reactor content show a43% conversion of propylene to oxygenated products including methylfor-mate, about 24% of propylene oxide, methanol, water and carbondioxide.

Example XI To a pressure reactor of the type described above is charged30 g. of4-methyl-5-(1,1-dimethyl-2,2,2-trichloro)ethyl-2-oxo-1,3-dioxolane, 13g. of acetaldehyde as an initiator, and about 5 g. of ethylene. Thesealed reactor is attached to an agitator assembly and immersed in a hotoil bath of 220 C. When thermal equilibrium is established within thereactor, oxygen is introduced to a total overpressure of 200 p.s.i.g.The oxidation is carried on for about 7 minutes, then the oxygen is shutoff and the reactor is immersed in a cold water bath. Analyses indicatea 15% conversion of ethylene to oxygenated products including about 23%ethylene oxide.

Example XII To a similar reactor is charged 25 g. of4-trifluoromethyl-2-oxo-1,3-dioxolane, drops of acetaldehyde as aninitiator, and about 6 g. of Z-methyl-Z-butene. The sealed reactor isattached to an agitator assembly and immersed in an oil bath at 150 C.When thermal equilibrium is reached within the reactor, an oxygenoverpressure of 200 p.'s.-i.g. is introduced to initiate the reactionfollowed after a 2 minute interval by an additional 100 p.s.i.g.overpressure of oxygen. After a total reaction period of about 8minutes, oxygen addition is stopped, and the reactor is cooled in a coldwater bath. Analyses indicate a 35% conversion of olefin to oxygenatedproducts with a major product being 2-methyl-2,3- epoxybutane obtainedin about 49% yield.

Example XIII conversion of olefin to oxygenated products among' styreneoxide is a major constituent.

Example XIV To a Hoke pressure reactor is charged4,4,5,5-tetramethyl-2-oxo-1,3-dioxolane, acetaldehyde initiator, andbutadiene. The sealed reactor is attached to an agitator assembly andimmersed in an oil bath at 175 C. After thermal equilibrium is attained,oxygen is introduced to a total overpressure of 200 p.s.i.g. over areaction interval of about 10 minutes. The oxygen is then shut oil andthe reactor is cooled by immersion in a cold water bath. Analysesindicate a 57 conversion of olefin to oxygenated products containingbutadiene oxide in about 17% yield.

Various other modifications of the instant invention will be apparent tothose skilled in the art without departing from the spirit and scopethereof.

I claim.

1. Process for the preparation of olefin oxides which comprisesoxidizing an epoxidizable olefinically unsaturated hydrocarbon compoundhaving up to 18 carbon atoms with molecular oxygen at a temperaturewithin the range of from C. to 350 C. and pressures within the range offrom 0.5 to 350 atmospheres in a liquid reaction medium consistingessentially of an ester selected from the group consisting of carbonicacid esters having the formulae:

and mixtures thereof, wherein R, R and R are selected from the groupconsisting of hydrogen, straight chain alkyl and haloalkyl groups havingfrom 1 to 3 carbon atoms and straight chain alkyl and haloalkyl groupshaving from 1 to 3 carbon atoms having as substituents on other than theterminal carbon atom thereof a member selected from the group consistingof alkyl and haloalkyl groups having from 1 to 3 carbon atoms, providedthat the carbon atoms to which the R, R and R" groups are attached havenot more than one methylene group attached thereto.

2. Process according to claim 1 wherein the oxidation occurs in theabsence of added catalysts.

3. Process for the preparation of propylene oxide which comprisesoxidizing propylene with molecular oxygen at a temperature within therange of from C. to 250 C. and a pressure within the range of from 6 toatmospheres in a liquid reaction medium as described in claim 1.

4. Process according to claim 3 wherein said reaction medium consistsessentially of dimethyl carbonate.

5. Process according to; claim 3 wherein said reaction medium isethylene carbonate.

6. Process according to claim 3 wherein said reaction medium is amixture of carbonic acid esters.

7. Process according to claim 6 wherein said reaction medium is amixture of dimethyl carbonate and ethylene carbonate.

8. Process according to claim 3 wherein said reaction medium consistsessentially of 4-methyl-2-oxo-1,3-dioxolane.

References Cited by the Examiner UNITED STATES PATENTS 2,475,605 7/1949Prutton et al. 260-451 2,784,202 3/1957 Gardner et al. Z60348.52,985,668 5/1961 Shingu 260-3485 OTHER REFERENCES Bergmann, TheChemistry of Acetylene and Related Compounds, page 80, IntersciencePublishers, Inc., New York (1948).

Durrans, T. H., Solvents, 7th ed. (1957), pp. XV, 128446.

WALTER A. MODANCE, Primary Examiner.

NICHOLAS RIZZO, Examiner.

1. PROCESS FOR THE PREPARATION OF OLEFIN OXIDES WHICH COMPRISESOXIDIZING AN EPOXIDIZABLE OLEFINICALLY UNSATURATED HYDROCARBON COMPOUNDHAVING UP TO 18 CARBON ATOMS WITH MOLECULAR OXYGEN AT A TEMPERATUREWITHIN THE RANGE OF FROM 80*C. TO 350*C. AND PRESSURES WITHIN THE RANGEOF FROM 0.5 TO 350 ATMOSPHERES IN A LIQUID REACTION MEDIUM CONSISTINGESSENTIALLY OF AN ESTER SELECTED FROM THE GROUP CONSISTING OF CARBONICACID ESTERS HAVING THE FORMULAE: